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我来自螃蟹星球 · 2021年03月18日

问一道题:NO.PZ2018101001000054 [ CFA II ]

问题如下:

Allen wants to predict the sales volume of his shop in December 20X8, so he uses sales volume of January 20X7 to November 20X8 as samples to make a linear trend model and gets the following result: Y ^ t  =264.75+2.58t. And it also shows that the Durbin-Watson statistic of this model is 1.0384.

Given the critical values at the 0.05 significance level for the Durbin-Watson statistic are Dl=1.26 and Du=1.44. Which of the followings is most likely correct?

选项:

A.

There exists a negative serial correlation in the errors.

B.

There exists a positive serial correlation in the errors.

C.

There exists no serial correlation in the errors.

解释:

B is correct.

考点: Linear trend model & log-linear trend model.

解析: 本题考的是对该线性趋势模型所做的DW检验 。 这道题已经给出了DW统计量和两个临界值点 , 已知DW统计量=1.0384是小于Dl=1.26的 , 就可以得出这个序列相关是正序列相关的结论 。 所以B选项正确 。

请问题目中说critical value是0.05是一个干扰项吗?我直接用0.05=1.65来算就判断错了

3 个答案

星星_品职助教 · 2021年03月18日

@我来自螃蟹星球

好的~题库里关于DW test还有几道非常类似的题目,可以都练练,如果有问题可以继续提问~

我来自螃蟹星球 · 2021年03月18日

谢谢,我弄混了

星星_品职助教 · 2021年03月18日

同学你好,

题干描述为:“....the critical values at the 0.05 significance level ...... are Dl=1.26 and Du=1.44”。所以这里的0.05是significance level的水平,相当于α=5%。并不是关键值。关键值是后面的1.26和1.44。

0.05在这道题里没什么用。

此外,这道题是DW test,所以用的也是DW的关键值(1.26和1.44),不能用1.65(正态分布/z-test下的关键值)



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